Packaging for telecommunications, computers and electronic systems has continued to decrease in overall size while increasing in functionality. This has resulted in an increase in the density of input/output (I/O) interconnects, creating a demand for fine pitch (0.050 inch spacings and less) connectors to meet limited space constraints.
A variety of interface standards exist today in an effort to maintain compatibility and uniformity when interconnecting computers to printers, drives, and other peripheral devices. Due to the need for increased signal speeds, controlled impedance, and electrical shielding, and while reducing overall size and weight, a new generation of 0.050 inch pitch connectors are beginning to replace the RS-232 type D subminiature connectors which have traditionally been used in these applications. The Small Computer Systems Interface (SCSI) specification has been developed which controls the electrical characteristics of the connecting cable and outlines the mating face of the interconnects. The contact pin layout is shown in FIG. 1, which is defined by two rows, spaced 0.100 inch apart with a contact pitch of 0.050 inch. In order to maintain this fine pitch, certain connector designs have utilized discrete wire insulation displacement contact (IDC) technology.
IDC technology has been an efficient, cost effective method for mass-termination of cables to connectors for many years. The advantage stems, in part, from the ribbon cable design. Orientation of the cable conductors in a uniform row provides strain relief through support from adjacent conductors, typically yielding good electrical performance. When using IDC technology with discrete wire cable applications, some of these advantages are lost. Conductors must be individually terminated, thus eliminating the inherent strain relief. Unless individual contacts have integral strain relief, excessive wire movement can cause large changes in contact resistance or even result in open circuits caused by a loss of the gas tight IDC termination. It thus becomes difficult in fine pitch applications to include an integral strain relief for IDC type contacts.
Crimping discrete wire conductors to contact terminals has also been a cost effective method for high reliable interconnects for years. This technology is advantageous in providing integral contact strain relief, gas tight termination and low installed cost. Because of these advantages, crimp style contact designs are widely used in a variety of cable applications, generally having contact spacings of 0.090 inch and greater. Providing a crimp contact design on 0.050 pitch which adheres to the layout dimensions shown in FIG. 1, has resulted in design difficulties.
Such design difficulties result from a desire to have a contact crimp geometry which would provide a reliable electrical integrity for a range of wire sizes, while adhering to the tight contact spacing requirements. Contradicting this approach is the need to maintain sufficient wall thicknesses in the electrical connector insulative housing of sufficient size and strength to enable mold processability, dielectric strength and overall mechanical stability.